The organs of plants have different functions and the allocation ratio of organ biomass is closely related to the ability to obtain resources for the plants.Plants organs present allometric phenomena during growth and development.By simulating the growth characteristic of Chenopodium acuminatum in different densities (16,44.4,100,and 400 plants/m²),we used allometry analysis to study the effects of density on the biomass allocation and allometric growth of C.acuminatum.The results showed that,with the increase of density,there were different levels of competition for both aboveground and belowground organs,ie.,the distribution of root and main stem increased,and the distribution of stem and aboveground organs decreased,but the distribution of leaves and reproductive organs did not change with the density.There were significant allometric relationships between each pair organs.The changes of leaves vs.main stem,root vs.aboveground organs,root vs.stem,root vs.main stem,reproductive vs.aboveground organs,and reproductive vs.root of biomass were not affected by the density,with these exhibiting ‘apparent’ plasticity.The allometric relationships of biomass in leaves vs.aboveground organs,leaves vs.root,leaves vs.stem,stem vs.aboveground organs,main stem vs.aboveground organs,reproductive organs vs.stem,and reproductive organs vs.main stem were significantly affected by density,representing ‘true’ plasticity.The results showed that density could affect the growth of C.acuminatum.The allometric index of biomass between leaves vs.main stem,leaves vs.root and main stem vs.aboveground organs in 400 plants/m² was close to 3/4,which is in accord with the metabolic theory of ecology,while the allometric indexes were significantly (P<0.001) different from 3/4 among other densities.This suggests that the plants with complete competition are more likely to conform to the predictions of metabolic theory,while plants with weak competition exhibit species-specific resource investment.